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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 11 commits: Fix determinism of linker arguments
by Marge Bot (＠marge-bot) 04 Mar '26

04 Mar '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 8b34e4ce by Ilias Tsitsimpis at 2026-03-04T09:42:26-05:00 Fix determinism of linker arguments The switch from Data.Map to UniqMap in 3b5be05ac29 introduced non-determinism in the order of packages passed to the linker. This resulted in non-reproducible builds where the DT_NEEDED entries in dynamic libraries were ordered differently across builds. Fix the regression by explicitly sorting the package list derived from UniqMap. Fixes #26838 - - - - - 9bb6323a by Matthew Pickering at 2026-03-04T09:42:28-05:00 determinism: Use a deterministic renaming when writing bytecode files Now when writing the bytecode file, a counter and substitution are used to provide deterministic keys to local variables (rather than relying on uniques). This change ensures that `.gbc` are produced deterministically. Fixes #26499 - - - - - df59365d by Teo Camarasu at 2026-03-04T09:42:30-05:00 ghc-internal: delete Version hs-boot loop Version has a Read instance which needs Unicode but part of the Unicode interface is the unicode version. This is easy to resolve. We simply don't re-export the version from the Unicode module. Resolves #26940 - - - - - 1d1ad339 by Sylvain Henry at 2026-03-04T09:43:02-05:00 Linker: implement support for COMMON symbols (#6107) Add some support for COMMON symbols. We don't support common symbols having different sizes where the larger one is allocated after the smaller one. The linker will fail with an appropriate error message if it happens. - - - - - c12bedae by Duncan Coutts at 2026-03-04T09:43:14-05:00 Apply NOINLINE pragmas to generated Typeable bindings For context, see the existing Note [Grand plan for Typeable] and the Note [NOINLINE on generated Typeable bindings] added in the subsequent commit. This is about reducing the number of exported top level names and unfoldings, which reduces interface file sizes and reduces the number of global/dynamic linker symbols. - - - - - 36631175 by Duncan Coutts at 2026-03-04T09:43:15-05:00 Add documentation Note [NOINLINE on generated Typeable bindings] and refer to it from the code and existing documentation. - - - - - 103374c4 by Duncan Coutts at 2026-03-04T09:43:15-05:00 Switch note to "named wrinkle" style, (GPT1)..(GPT7) GPT = Grand plan for Typeable - - - - - 9142dc12 by Duncan Coutts at 2026-03-04T09:43:15-05:00 Accept test output and metric decreases for Typeable NOINLINE Tests that record the phase output for type checking or for simplifier end up with different output: the generated bindings now have an Inline [~] annotation, and many top level names are now local rather than module-prefixed for export. Also accept the numerous metric decreases in compile_time/bytes allocated, and a few in compile_time/max_bytes_used. There's also one instance of a decrease in runtime/max_bytes_used but it's a ghci-way test and so presumably the reason is that it loads smaller .hi files and/or links fewer symbols. ------------------------- Metric Decrease: CoOpt_Singletons MultiLayerModulesTH_OneShot MultilineStringsPerf T10421 T10547 T12150 T12227 T12234 T12425 T13035 T13056 T13253 T13253-spj T15703 T16875 T17836b T17977b T18140 T18223 T18282 T18304 T18698a T18698b T18730 T18923 T20049 T21839c T24471 T24582 T24984 T3064 T4029 T5030 T5642 T5837 T6048 T9020 T9198 T9961 WWRec hard_hole_fits mhu-perf ------------------------- - - - - - 22b9805c by Cheng Shao at 2026-03-04T09:43:16-05:00 compiler: fix redundant import of GHC.Hs.Lit This patch removes a redundant import of `GHC.Hs.Lit` which causes a ghc build failure with validate flavours when bootstrapping from 9.14. Fixes #26972. - - - - - e3550962 by Cheng Shao at 2026-03-04T09:43:17-05:00 compiler: avoid unneeded traversals in GHC.Unit.State Following !15591, this patch avoids unneeded traversals in `reportCycles`/`reportUnusable` when log verbosity is below given threshold. Also applies `logVerbAtLeast` when appropriate. Co-authored-by: Codex <codex(a)openai.com> - - - - - 188d58e1 by Cheng Shao at 2026-03-04T09:43:17-05:00 ghc-internal: fix redundant import in GHC.Internal.Event.Windows.ManagedThreadPool This patch fixes redundant import in `GHC.Internal.Event.Windows.ManagedThreadPool` that causes a compilation error when building windows target with validate flavours and bootstrapping from 9.14. Fixes #26976. - - - - - 50 changed files: - compiler/GHC/ByteCode/Serialize.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Tc/Instance/Typeable.hs - compiler/GHC/Unit/State.hs - compiler/GHC/Utils/Error.hs - libraries/base/src/GHC/Unicode.hs - libraries/ghc-internal/ghc-internal.cabal.in - − libraries/ghc-internal/src/GHC/Internal/Data/Version.hs-boot - libraries/ghc-internal/src/GHC/Internal/Event/Windows/ManagedThreadPool.hs - libraries/ghc-internal/src/GHC/Internal/Unicode.hs - libraries/ghc-internal/src/GHC/Internal/Unicode/Version.hs - libraries/ghc-internal/tools/ucd2haskell/exe/UCD2Haskell/ModuleGenerators.hs - rts/Linker.c - rts/LinkerInternals.h - rts/linker/Elf.c - rts/linker/MachO.c - rts/linker/PEi386.c - testsuite/tests/deSugar/should_compile/T16615.stderr - testsuite/tests/deSugar/should_compile/T2431.stderr - testsuite/tests/dmdanal/should_compile/T16029.stdout - testsuite/tests/numeric/should_compile/T14170.stdout - testsuite/tests/numeric/should_compile/T14465.stdout - testsuite/tests/numeric/should_compile/T7116.stdout - testsuite/tests/roles/should_compile/Roles1.stderr - testsuite/tests/roles/should_compile/Roles13.stderr - testsuite/tests/roles/should_compile/Roles14.stderr - testsuite/tests/roles/should_compile/Roles2.stderr - testsuite/tests/roles/should_compile/Roles3.stderr - testsuite/tests/roles/should_compile/Roles4.stderr - testsuite/tests/roles/should_compile/T8958.stderr - testsuite/tests/rts/linker/Makefile - + testsuite/tests/rts/linker/T6107.hs - + testsuite/tests/rts/linker/T6107.stdout - + testsuite/tests/rts/linker/T6107_sym1.s - + testsuite/tests/rts/linker/T6107_sym2.s - testsuite/tests/rts/linker/all.T - testsuite/tests/simplCore/should_compile/OpaqueNoCastWW.stderr - testsuite/tests/simplCore/should_compile/T3717.stderr - testsuite/tests/simplCore/should_compile/T3772.stdout - testsuite/tests/simplCore/should_compile/T4908.stderr - testsuite/tests/simplCore/should_compile/T4930.stderr - testsuite/tests/simplCore/should_compile/T7360.stderr - testsuite/tests/simplCore/should_compile/T8274.stdout - testsuite/tests/simplCore/should_compile/T9400.stderr - testsuite/tests/simplCore/should_compile/noinline01.stderr - testsuite/tests/simplCore/should_compile/par01.stderr - testsuite/tests/th/TH_Roles2.stderr - testsuite/tests/typecheck/should_compile/T13032.stderr - testsuite/tests/typecheck/should_compile/T18406b.stderr - testsuite/tests/typecheck/should_compile/T18529.stderr The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1207510970d873388cd5985f3ed283… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1207510970d873388cd5985f3ed283… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/int-index/out-of-scope] WIP: Refactor
by Vladislav Zavialov (＠int-index) 04 Mar '26

04 Mar '26

Vladislav Zavialov pushed to branch wip/int-index/out-of-scope at Glasgow Haskell Compiler / GHC Commits: 5f6bef91 by Vladislav Zavialov at 2026-03-04T17:25:09+03:00 WIP: Refactor - - - - - 5 changed files: - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Gen/Head.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Tc/Utils/TcMType.hs - testsuite/tests/rename/should_fail/RnStaticPointersFail02.stderr Changes: ===================================== compiler/GHC/Tc/Errors.hs ===================================== @@ -5,7 +5,7 @@ module GHC.Tc.Errors( reportUnsolved, reportAllUnsolved, warnAllUnsolved, warnDefaulting, - mkDelayedErrorTerm, + pprDeferredTypeError, -- * GHC API helper functions solverReportMsg_ExpectedActuals, mismatchMsg_ExpectedActuals @@ -1387,19 +1387,15 @@ mkErrorTerm ct_loc ty ctxt msg supp hints supp hints -- This will be reported at runtime, so we always want "error:" in the report, never "warning:" - ; mkDelayedErrorTerm ty msg } - -mkDelayedErrorTerm - :: Type -- of the error term - -> MsgEnvelope TcRnMessage - -> TcM EvTerm -mkDelayedErrorTerm ty msg - = do { dflags <- getDynFlags - ; let err_msg = pprLocMsgEnvelope (initTcMessageOpts dflags) msg - err_str = showSDoc dflags $ - err_msg $$ text "(deferred type error)" - - ; return $ evDelayedError ty err_str } + ; dflags <- getDynFlags + ; let err_msg = pprDeferredTypeError dflags msg + ; return $ evDelayedError ty err_msg } + +pprDeferredTypeError :: DynFlags -> MsgEnvelope TcRnMessage -> String +pprDeferredTypeError dflags msg = + let err_msg = pprLocMsgEnvelope (initTcMessageOpts dflags) msg + in showSDoc dflags $ + err_msg $$ text "(deferred type error)" tryReporters :: SolverReportErrCtxt -> [ReporterSpec] -> [ErrorItem] -> TcM (SolverReportErrCtxt, [ErrorItem]) -- Use the first reporter in the list whose predicate says True ===================================== compiler/GHC/Tc/Gen/Head.hs ===================================== @@ -39,7 +39,7 @@ import GHC.Tc.Utils.Unify import GHC.Tc.Utils.Instantiate import GHC.Tc.Instance.Family ( tcLookupDataFamInst ) import GHC.Tc.Errors.Types -import GHC.Tc.Errors +import GHC.Tc.Errors ( pprDeferredTypeError ) import GHC.Tc.Solver ( InferMode(..), simplifyInfer ) import GHC.Tc.Utils.Env import GHC.Tc.Utils.TcMType @@ -832,20 +832,18 @@ tc_infer_id (L loc qnm@(WithUserRdr rdr id_name)) | otherwise = ErrorWithoutFlag msg <- mk_msg reason addDiagnosticTc msg - if defer_out_of_scope then msg_to_hole msg else failM + msg_to_hole msg msg_to_hole :: TcRnMessage -> TcM (HsExpr GhcTc, TcType) msg_to_hole msg = do - loc <- getSrcSpanM - let locc = L (noAnnSrcSpan loc) rdr - ty <- newOpenFlexiTyVarTy - u <- newUnique - msg_envelope <- mkTcRnMessage loc msg - delayed_err <- mkDelayedErrorTerm ty msg_envelope - ref <- newTcRef delayed_err + dflags <- getDynFlags + let lrdr = L loc rdr + msg_envelope <- mkTcRnMessage (locA loc) msg + let err_msg = pprDeferredTypeError dflags msg_envelope + ty <- newOpenFlexiTyVarTy + her <- newExprHoleRef ty (evDelayedError ty err_msg) tcEmitBindingUsage bottomUE -- Holes fit any usage environment (#18491) - let her = HER ref ty u - return (HsHole (HoleVar locc, her), ty) + return (HsHole (HoleVar lrdr, her), ty) {- Note [Overview of assertions] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ===================================== compiler/GHC/Tc/Utils/Env.hs ===================================== @@ -402,7 +402,6 @@ mkIllegalTyVarMessage :: DiagnosticReason -> WithUserRdr Name -> TcM TcRnMessage fail_with_msg :: DiagnosticReason -> WhatLooking -> NameSpace -> RdrName -> Name -> Maybe TermLevelUseCtxt -> TermLevelUseErr -> TcM TcRnMessage fail_with_msg reason what_looking whatName rdr nm pprov err = do - -- defer_out_of_scope <- goptM Opt_DeferOutOfScopeVariables (imp_errs, hints) <- get_suggestions what_looking whatName rdr hfdc <- getHoleFitDispConfig unit_state <- hsc_units <$> getTopEnv ===================================== compiler/GHC/Tc/Utils/TcMType.hs ===================================== @@ -45,6 +45,8 @@ module GHC.Tc.Utils.TcMType ( emitWantedEqs, emitNewExprHole, newTcEvBinds, newNoTcEvBinds, addTcEvBind, + newExprHoleRef, + newCoercionHole, fillCoercionHole, isFilledCoercionHole, checkCoercionHole, @@ -314,6 +316,12 @@ emitNewExprHole occ ty ; emitHole hole ; return her } +newExprHoleRef :: Type -> EvTerm -> TcM HoleExprRef +newExprHoleRef ty ev + = do { u <- newUnique + ; ref <- newTcRef ev + ; return $ HER ref ty u } + newDict :: Class -> [TcType] -> TcM DictId newDict cls tys = do { name <- newSysName (mkDictOcc (getOccName cls)) ===================================== testsuite/tests/rename/should_fail/RnStaticPointersFail02.stderr ===================================== @@ -1,3 +1,9 @@ +RnStaticPointersFail02.hs:5:5: error: [GHC-39999] + • No instance for ‘ghc-internal-9.1500.0:GHC.Internal.Data.Typeable.Internal.Typeable + t0’ + arising from a static form + • In the expression: static T + In an equation for ‘f’: f = static T RnStaticPointersFail02.hs:5:12: error: [GHC-01928] • Illegal term-level use of the type constructor ‘T’ @@ -5,3 +11,4 @@ RnStaticPointersFail02.hs:5:12: error: [GHC-01928] • In the body of a static form: T In the expression: static T In an equation for ‘f’: f = static T + View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5f6bef914e323c9e42efff914d6050a… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5f6bef914e323c9e42efff914d6050a… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/andreask/ww_cbv_docs
by Andreas Klebinger (＠AndreasK) 04 Mar '26

04 Mar '26

Andreas Klebinger pushed new branch wip/andreask/ww_cbv_docs at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/andreask/ww_cbv_docs You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/fendor/linkable-usage] Record `LinkableUsage` instead of `Linkable` in `LoaderState`
by Hannes Siebenhandl (＠fendor) 04 Mar '26

04 Mar '26

Hannes Siebenhandl pushed to branch wip/fendor/linkable-usage at Glasgow Haskell Compiler / GHC Commits: 884dba21 by fendor at 2026-03-04T14:34:09+01:00 Record `LinkableUsage` instead of `Linkable` in `LoaderState` Retaining a ByteCode `Linkable` after it has been loaded retains its `UnlinkedBCO`, keeping it alive for the remainder of the program. This starts accumulating a lot of `UnlinkedBCO` and memory over time. However, the `Linkable` is merely used to later record its usage in `mkObjectUsage`, which is used for recompilation checking. However, this is incorrect, as the interface file and bytecode objects could be in different states, e.g. the interface changes, but the bytecode library hasn't changed so we don't need to recompile and vice versa. By computing a `Fingerprint` for the `ModuleByteCode`, and recording it in the `LinkableUsage`, we know precisely whether the `ByteCode` object on disk is outdated. Thus, parts of this commit just makes sure that we efficiently compute a `Fingerprint` for `ModuleByteCode` and store it in the on-disk representation of `ModuleByteCode`. We change the `LoaderState` to retain `LinkableUsage`, which is smaller representation of a `Linkable`. This allows us to free the unneeded fields of `Linkable` after linking them. We declare the following memory invariants that this commit implements: * No `LinkablePart` should be retained from `LoaderState`. * `Linkable`s should be unloaded after they have been loaded. These invariants are unfortunately tricky to automatically uphold, so we are simply documenting our assumptions for now. ------------------------- Metric Increase: MultiLayerModulesTH_OneShot ------------------------- We allocate a bit more, but the peak number of bytes doesn't change. While a bit unfortunate, accepting the metric increase. We add multiple new performance measurements where we were able to observe the desired memory invariants. Further, we add regression tests to validate that the recompilation checker behaves more correct than before. - - - - - 32 changed files: - + compiler/GHC/ByteCode/Binary.hs - + compiler/GHC/ByteCode/Recomp/Binary.hs - compiler/GHC/ByteCode/Serialize.hs - compiler/GHC/Driver/Hooks.hs - compiler/GHC/Driver/Main.hs - compiler/GHC/Driver/Pipeline.hs - compiler/GHC/Driver/Plugins.hs - compiler/GHC/HsToCore/Usage.hs - compiler/GHC/Iface/Recomp.hs - compiler/GHC/Iface/Recomp/Types.hs - compiler/GHC/Linker/ByteCode.hs - compiler/GHC/Linker/Deps.hs - compiler/GHC/Linker/Loader.hs - compiler/GHC/Linker/Types.hs - compiler/GHC/Runtime/Loader.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Unit/Home/ModInfo.hs - compiler/GHC/Unit/Module/Deps.hs - compiler/GHC/Unit/Module/Status.hs - compiler/GHC/Utils/Binary.hs - compiler/ghc.cabal.in - ghc/GHCi/Leak.hs - + testsuite/ghc-config/ghc-config - + testsuite/tests/bytecode/TLinkable/Makefile - + testsuite/tests/bytecode/TLinkable/all.T - + testsuite/tests/bytecode/TLinkable/genSplices - + testsuite/tests/bytecode/TLinkable/genSplices2 - + testsuite/tests/bytecode/TLinkable/linkable_bytecodelib.stdout - testsuite/tests/count-deps/CountDepsAst.stdout - testsuite/tests/count-deps/CountDepsParser.stdout - testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp_th.stdout The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/884dba21c5f56e71ce2e7fa59737f2b… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/884dba21c5f56e71ce2e7fa59737f2b… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/andreask/inlineable_docs
by Andreas Klebinger (＠AndreasK) 04 Mar '26

04 Mar '26

Andreas Klebinger pushed new branch wip/andreask/inlineable_docs at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/andreask/inlineable_docs You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/io-manager-deadlock-detection] FIXUP: Make the IOManager API use CapIOManager rather than Capability
by Duncan Coutts (＠dcoutts) 04 Mar '26

04 Mar '26

Duncan Coutts pushed to branch wip/io-manager-deadlock-detection at Glasgow Haskell Compiler / GHC Commits: ac791614 by Duncan Coutts at 2026-03-04T10:58:13+00:00 FIXUP: Make the IOManager API use CapIOManager rather than Capability We had updated the type of appendToIOBlockedQueue, but had not updated the CMM call sites. It makes one realise that sometimes C's primitive type system is useful! - - - - - 1 changed file: - rts/PrimOps.cmm Changes: ===================================== rts/PrimOps.cmm ===================================== @@ -2351,7 +2351,8 @@ stg_asyncReadzh ( W_ fd, W_ is_sock, W_ len, W_ buf ) ASSERT(StgTSO_why_blocked(CurrentTSO) == NotBlocked::I32); %release StgTSO_why_blocked(CurrentTSO) = BlockedOnRead::I32; - ccall appendToIOBlockedQueue(MyCapability() "ptr", CurrentTSO "ptr"); + ccall appendToIOBlockedQueue(Capability_iomgr(MyCapability()) "ptr", + CurrentTSO "ptr"); jump stg_block_async(); #endif } @@ -2377,7 +2378,8 @@ stg_asyncWritezh ( W_ fd, W_ is_sock, W_ len, W_ buf ) ASSERT(StgTSO_why_blocked(CurrentTSO) == NotBlocked::I32); %release StgTSO_why_blocked(CurrentTSO) = BlockedOnWrite::I32; - ccall appendToIOBlockedQueue(MyCapability() "ptr", CurrentTSO "ptr"); + ccall appendToIOBlockedQueue(Capability_iomgr(MyCapability()) "ptr", + CurrentTSO "ptr"); jump stg_block_async(); #endif } @@ -2403,7 +2405,8 @@ stg_asyncDoProczh ( W_ proc, W_ param ) ASSERT(StgTSO_why_blocked(CurrentTSO) == NotBlocked::I32); %release StgTSO_why_blocked(CurrentTSO) = BlockedOnDoProc::I32; - ccall appendToIOBlockedQueue(MyCapability() "ptr", CurrentTSO "ptr"); + ccall appendToIOBlockedQueue(Capability_iomgr(MyCapability()) "ptr", + CurrentTSO "ptr"); jump stg_block_async(); #endif } View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/ac79161475ca41f462e6b1ff66e6410… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/ac79161475ca41f462e6b1ff66e6410… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 8 commits: Fix determinism of linker arguments
by Marge Bot (＠marge-bot) 03 Mar '26

03 Mar '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 84b66b4d by Ilias Tsitsimpis at 2026-03-04T02:38:57-05:00 Fix determinism of linker arguments The switch from Data.Map to UniqMap in 3b5be05ac29 introduced non-determinism in the order of packages passed to the linker. This resulted in non-reproducible builds where the DT_NEEDED entries in dynamic libraries were ordered differently across builds. Fix the regression by explicitly sorting the package list derived from UniqMap. Fixes #26838 - - - - - 07dac97f by Matthew Pickering at 2026-03-04T02:38:58-05:00 determinism: Use a deterministic renaming when writing bytecode files Now when writing the bytecode file, a counter and substitution are used to provide deterministic keys to local variables (rather than relying on uniques). This change ensures that `.gbc` are produced deterministically. Fixes #26499 - - - - - 5919ed75 by Teo Camarasu at 2026-03-04T02:39:00-05:00 ghc-internal: delete Version hs-boot loop Version has a Read instance which needs Unicode but part of the Unicode interface is the unicode version. This is easy to resolve. We simply don't re-export the version from the Unicode module. Resolves #26940 - - - - - ed4663ec by Wolfgang Jeltsch at 2026-03-04T02:39:02-05:00 Remove in-package dependencies on `GHC.Internal.System.IO` This contribution eliminates all dependencies on `GHC.Internal.System.IO` from within `ghc-internal`. It comprises the following changes: * Make `GHC.Internal.Fingerprint` independent of I/O support * Tighten the dependencies of `GHC.Internal.Data.Version` * Tighten the dependencies of `GHC.Internal.TH.Monad` * Tighten the dependencies of `GHCi.Helpers` * Move some code that needs `System.IO` to `template-haskell` * Move the `GHC.ResponseFile` implementation into `base` * Move the `System.Exit` implementation into `base` * Move the `System.IO.OS` implementation into `base` Metric Decrease: size_hello_artifact size_hello_artifact_gzip size_hello_unicode size_hello_unicode_gzip - - - - - 64fa6d67 by Sylvain Henry at 2026-03-04T02:39:09-05:00 Linker: implement support for COMMON symbols (#6107) Add some support for COMMON symbols. We don't support common symbols having different sizes where the larger one is allocated after the smaller one. The linker will fail with an appropriate error message if it happens. - - - - - 698647cb by Cheng Shao at 2026-03-04T02:39:10-05:00 compiler: fix redundant import of GHC.Hs.Lit This patch removes a redundant import of `GHC.Hs.Lit` which causes a ghc build failure with validate flavours when bootstrapping from 9.14. Fixes #26972. - - - - - 3e101535 by Cheng Shao at 2026-03-04T02:39:11-05:00 compiler: avoid unneeded traversals in GHC.Unit.State Following !15591, this patch avoids unneeded traversals in `reportCycles`/`reportUnusable` when log verbosity is below given threshold. Also applies `logVerbAtLeast` when appropriate. Co-authored-by: Codex <codex(a)openai.com> - - - - - 12075109 by Cheng Shao at 2026-03-04T02:39:12-05:00 ghc-internal: fix redundant import in GHC.Internal.Event.Windows.ManagedThreadPool This patch fixes redundant import in `GHC.Internal.Event.Windows.ManagedThreadPool` that causes a compilation error when building windows target with validate flavours and bootstrapping from 9.14. Fixes #26976. - - - - - 35 changed files: - compiler/GHC/ByteCode/Serialize.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Unit/State.hs - compiler/GHC/Utils/Error.hs - libraries/base/src/GHC/Fingerprint.hs - libraries/base/src/GHC/ResponseFile.hs - libraries/base/src/GHC/Unicode.hs - libraries/base/src/System/Exit.hs - libraries/base/src/System/IO/OS.hs - libraries/ghc-heap/GHC/Exts/Heap/Closures.hs - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/src/GHC/Internal/Data/Version.hs - − libraries/ghc-internal/src/GHC/Internal/Data/Version.hs-boot - libraries/ghc-internal/src/GHC/Internal/Event/Windows/ManagedThreadPool.hs - libraries/ghc-internal/src/GHC/Internal/Fingerprint.hs - libraries/ghc-internal/src/GHC/Internal/GHCi/Helpers.hs - − libraries/ghc-internal/src/GHC/Internal/ResponseFile.hs - − libraries/ghc-internal/src/GHC/Internal/System/Exit.hs - − libraries/ghc-internal/src/GHC/Internal/System/IO/OS.hs - libraries/ghc-internal/src/GHC/Internal/TH/Monad.hs - libraries/ghc-internal/src/GHC/Internal/Unicode.hs - libraries/ghc-internal/src/GHC/Internal/Unicode/Version.hs - libraries/ghc-internal/tools/ucd2haskell/exe/UCD2Haskell/ModuleGenerators.hs - libraries/template-haskell/Language/Haskell/TH/Syntax.hs - rts/Linker.c - rts/LinkerInternals.h - rts/linker/Elf.c - rts/linker/MachO.c - rts/linker/PEi386.c - testsuite/tests/rts/linker/Makefile - + testsuite/tests/rts/linker/T6107.hs - + testsuite/tests/rts/linker/T6107.stdout - + testsuite/tests/rts/linker/T6107_sym1.s - + testsuite/tests/rts/linker/T6107_sym2.s - testsuite/tests/rts/linker/all.T The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/055d865255ec949fb2bcfbfad9c1a1… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/055d865255ec949fb2bcfbfad9c1a1… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/backports-9.12.4] 6 commits: Fix a horrible shadowing bug in implicit parameters
by Zubin (＠wz1000) 03 Mar '26

03 Mar '26

Zubin pushed to branch wip/backports-9.12.4 at Glasgow Haskell Compiler / GHC Commits: 451c6a43 by Simon Peyton Jones at 2026-03-04T12:15:09+05:30 Fix a horrible shadowing bug in implicit parameters Fixes #26451. The change is in GHC.Tc.Solver.Monad.updInertDicts where we now do /not/ delete /Wanted/ implicit-parameeter constraints. This bug has been in GHC since 9.8! But it's quite hard to provoke; I contructed a tests in T26451, but it was hard to do so. (cherry picked from commit c052c724d2dfc994994b6548545836969aee8ed8) - - - - - 85b0aae2 by Simon Peyton Jones at 2026-03-04T12:15:09+05:30 Fix subtle bug in GHC.Core.Utils.mkTick This patch fixes a decade-old bug in `mkTick`, which could generate type-incorrect code! See the diagnosis in #26772. The new code is simpler and easier to understand. (As #26772 says, I think it could be improved further.) (cherry picked from commit cbe4300ef586c8bee1800426624db12e0237c6b5) - - - - - 55885e4b by Simon Peyton Jones at 2026-03-04T12:15:09+05:30 Fix long-standing interaction between ticks and casts The code for Note [Eliminate Identity Cases] was simply wrong when ticks and casts interacted. This patch fixes the interaction. It was shown up when validating #26772, although it's not the exactly the bug that's reported by #26772. Nor is it easy to reproduce, hence no regression test. (cherry picked from commit b579dfdc614e288b0fd754ac69ae7ff723d808be) - - - - - 4fdab7ca by sheaf at 2026-03-04T12:15:09+05:30 NamedDefaults: require the class to be standard We now only default type variables if they only appear in constraints of the form `C v`, where `C` is either a standard class or a class with an in-scope default declaration. This rectifies an oversight in the original implementation of the NamedDefault extensions that was remarked in #25775; that implementation allowed type variables to appear in unary constraints which had arbitrary classes at the head. See the rewritten Note [How type-class constraints are defaulted] for details of the implementation. Fixes #25775 Fixes #25778 (cherry picked from commit f1acdd2c2b664ad0bdcaae4064b50e84aa7bc599) - - - - - cfbec95d by Rodrigo Mesquita at 2026-03-04T12:15:09+05:30 bytecode: Use 32bits for breakpoint index Fixes #26325 (cherry picked from commit e368e24779f8a7bf110a025383db23521b313407) - - - - - 7d22504b by Zubin Duggal at 2026-03-04T12:15:44+05:30 Prepare release 9.12.4 - - - - - 21 changed files: - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/Tc/Instance/Class.hs - compiler/GHC/Tc/Solver.hs - compiler/GHC/Tc/Solver/Dict.hs - compiler/GHC/Tc/Types/Evidence.hs - compiler/GHC/Types/DefaultEnv.hs - + docs/users_guide/9.12.4-notes.rst - docs/users_guide/release-notes.rst - libraries/base/base.cabal.in - libraries/base/changelog.md - rts/Disassembler.c - rts/Interpreter.c - + testsuite/tests/default/T25775.hs - + testsuite/tests/default/T25775.stderr - testsuite/tests/default/all.T - + testsuite/tests/typecheck/should_compile/T26451.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/T12921.stderr Changes: ===================================== compiler/GHC/ByteCode/Asm.hs ===================================== @@ -660,9 +660,22 @@ assembleI platform i = case i of tick_addr <- addr tick_mod info_addr <- addr info_mod np <- addr cc + let -- cast that checks that round-tripping through + -- Word32 doesn't change the value + toW32 x = let r = fromIntegral x :: Word32 + in if fromIntegral r == x + then r + else pprPanic "schemeER_wrk: breakpoint tick/info index too large!" (ppr x) + tick32 = toW32 tickx + tick_hi = fromIntegral (tick32 `shiftR` 16) + tick_lo = fromIntegral (tick32 .&. 0xffff) + info32 = toW32 infox + info_hi = fromIntegral (info32 `shiftR` 16) + info_lo = fromIntegral (info32 .&. 0xffff) emit bci_BRK_FUN [ Op p1 , Op tick_addr, Op info_addr - , SmallOp tickx, SmallOp infox + , SmallOp tick_hi, SmallOp tick_lo + , SmallOp info_hi, SmallOp info_lo , Op np ] ===================================== compiler/GHC/Core/Opt/Simplify/Iteration.hs ===================================== @@ -1731,6 +1731,7 @@ simplCast env body co0 cont0 , sc_hole_ty = coercionLKind co }) } -- NB! As the cast goes past, the -- type of the hole changes (#16312) + -- (f |> co) e ===> (f (e |> co1)) |> co2 -- where co :: (s1->s2) ~ (t1->t2) -- co1 :: t1 ~ s1 ===================================== compiler/GHC/Core/Opt/Simplify/Utils.hs ===================================== @@ -73,6 +73,7 @@ import GHC.Types.Tickish import GHC.Types.Demand import GHC.Types.Var.Set import GHC.Types.Basic +import GHC.Types.Name.Env import GHC.Data.OrdList ( isNilOL ) import GHC.Data.FastString ( fsLit ) @@ -82,9 +83,9 @@ import GHC.Utils.Monad import GHC.Utils.Outputable import GHC.Utils.Panic -import Control.Monad ( when ) +import Control.Monad ( guard, when ) import Data.List ( sortBy ) -import GHC.Types.Name.Env +import Data.Maybe import Data.Graph {- ********************************************************************* @@ -2471,7 +2472,27 @@ Note [Eliminate Identity Case] True -> True; False -> False -and similar friends. +and similar friends. There are some tricky wrinkles: + +(EIC1) Casts. We've seen this: + case e of x { _ -> x `cast` c } + And we definitely want to eliminate this case, to give + e `cast` c +(EIC2) Ticks. Similarly + case e of x { _ -> Tick t x } + At least if the tick is 'floatable' we want to eliminate the case + to give + Tick t e + +So `check_eq` strips off enclosing casts and ticks from the RHS of the +alternative, returning a wrapper function that will rebuild them around +the scrutinee if case-elim is successful. + +(EIC3) What if there are many alternatives, all identities. If casts + are involved they must be the same cast, to make the types line up. + In principle there could be different ticks in each RHS, but we just + pick the ticks from the first alternative. (In the common case there + is only one alternative.) Note [Scrutinee Constant Folding] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2665,45 +2686,47 @@ mkCase mode scrut outer_bndr alts_ty alts -- See Note [Eliminate Identity Case] -------------------------------------------------- -mkCase1 _mode scrut case_bndr _ alts@(Alt _ _ rhs1 : alts') -- Identity case - | all identity_alt alts +mkCase1 _mode scrut case_bndr _ (alt1 : alts) -- Identity case + | Just wrap <- identity_alt alt1 -- `wrap`: see (EIC1) and (EIC2) + , all (isJust . identity_alt) alts -- See (EIC3) in Note [Eliminate Identity Case] = do { tick (CaseIdentity case_bndr) - ; return (mkTicks ticks $ re_cast scrut rhs1) } + ; return (wrap scrut) } where - ticks = concatMap (\(Alt _ _ rhs) -> stripTicksT tickishFloatable rhs) alts' - identity_alt (Alt con args rhs) = check_eq rhs con args - - check_eq (Cast rhs co) con args -- See Note [RHS casts] - = not (any (`elemVarSet` tyCoVarsOfCo co) args) && check_eq rhs con args - check_eq (Tick t e) alt args - = tickishFloatable t && check_eq e alt args - - check_eq (Lit lit) (LitAlt lit') _ = lit == lit' - check_eq (Var v) _ _ | v == case_bndr = True - check_eq (Var v) (DataAlt con) args - | null arg_tys, null args = v == dataConWorkId con - -- Optimisation only - check_eq rhs (DataAlt con) args = cheapEqExpr' tickishFloatable rhs $ - mkConApp2 con arg_tys args - check_eq _ _ _ = False + identity_alt :: CoreAlt -> Maybe (CoreExpr -> CoreExpr) + identity_alt (Alt con args rhs) = check_eq con args rhs + + check_eq :: AltCon -> [Var] -> CoreExpr -> Maybe (CoreExpr -> CoreExpr) + -- (check_eq con args e) return True if + -- e looks like (Tick (Cast (Tick (con args)))) + -- where (con args) is the LHS of the alternative + -- In that case it returns (\e. Tick (Cast (Tick e))), + -- a wrapper function that can rebuild the tick/cast stuff + -- See (EIC1) and (EIC2) in Note [Eliminate Identity Case] + check_eq alt_con args (Cast e co) -- See (EIC1) + = do { guard (not (any (`elemVarSet` tyCoVarsOfCo co) args)) + ; wrap <- check_eq alt_con args e + ; return (flip mkCast co . wrap) } + check_eq alt_con args (Tick t e) -- See (EIC2) + = do { guard (tickishFloatable t) + ; wrap <- check_eq alt_con args e + ; return (Tick t . wrap) } + check_eq alt_con args e + | is_id alt_con args e = Just (\e -> e) + | otherwise = Nothing + + is_id :: AltCon -> [Var] -> CoreExpr -> Bool + is_id _ _ (Var v) | v == case_bndr = True + is_id (LitAlt lit') _ (Lit lit) = lit == lit' + is_id (DataAlt con) args rhs + | Var v <- rhs -- Optimisation only + , null arg_tys + , null args = v == dataConWorkId con + | otherwise = cheapEqExpr' tickishFloatable rhs $ + mkConApp2 con arg_tys args + is_id _ _ _ = False arg_tys = tyConAppArgs (idType case_bndr) - -- Note [RHS casts] - -- ~~~~~~~~~~~~~~~~ - -- We've seen this: - -- case e of x { _ -> x `cast` c } - -- And we definitely want to eliminate this case, to give - -- e `cast` c - -- So we throw away the cast from the RHS, and reconstruct - -- it at the other end. All the RHS casts must be the same - -- if (all identity_alt alts) holds. - -- - -- Don't worry about nested casts, because the simplifier combines them - - re_cast scrut (Cast rhs co) = Cast (re_cast scrut rhs) co - re_cast scrut _ = scrut - mkCase1 mode scrut bndr alts_ty alts = mkCase2 mode scrut bndr alts_ty alts ===================================== compiler/GHC/Core/Utils.hs ===================================== @@ -251,7 +251,7 @@ applyTypeToArgs pp_e op_ty args mkCastMCo :: CoreExpr -> MCoercionR -> CoreExpr mkCastMCo e MRefl = e -mkCastMCo e (MCo co) = Cast e co +mkCastMCo e (MCo co) = mkCast e co -- We are careful to use (MCo co) only when co is not reflexive -- Hence (Cast e co) rather than (mkCast e co) @@ -302,40 +302,41 @@ mkCast expr co -- | Wraps the given expression in the source annotation, dropping the -- annotation if possible. mkTick :: CoreTickish -> CoreExpr -> CoreExpr -mkTick t orig_expr = mkTick' id id orig_expr +mkTick t orig_expr = mkTick' id orig_expr where -- Some ticks (cost-centres) can be split in two, with the -- non-counting part having laxer placement properties. canSplit = tickishCanSplit t && tickishPlace (mkNoCount t) /= tickishPlace t + -- mkTick' handles floating of ticks *into* the expression. - -- In this function, `top` is applied after adding the tick, and `rest` before. - -- This will result in applications that look like (top $ Tick t $ rest expr). - -- If we want to push the tick deeper, we pre-compose `top` with a function - -- adding the tick. - mkTick' :: (CoreExpr -> CoreExpr) -- apply after adding tick (float through) - -> (CoreExpr -> CoreExpr) -- apply before adding tick (float with) - -> CoreExpr -- current expression + mkTick' :: (CoreExpr -> CoreExpr) -- Apply before adding tick (float with) + -- Always a composition of (Tick t) wrappers + -> CoreExpr -- Current expression -> CoreExpr - mkTick' top rest expr = case expr of + -- So in the call (mkTick' rest e), the expression + -- (rest e) + -- has the same type as e + -- Returns an expression equivalent to (Tick t (rest e)) + mkTick' rest expr = case expr of -- Float ticks into unsafe coerce the same way we would do with a cast. Case scrut bndr ty alts@[Alt ac abs _rhs] | Just rhs <- isUnsafeEqualityCase scrut bndr alts - -> top $ mkTick' (\e -> Case scrut bndr ty [Alt ac abs e]) rest rhs + -> Case scrut bndr ty [Alt ac abs (mkTick' rest rhs)] -- Cost centre ticks should never be reordered relative to each -- other. Therefore we can stop whenever two collide. Tick t2 e - | ProfNote{} <- t2, ProfNote{} <- t -> top $ Tick t $ rest expr + | ProfNote{} <- t2, ProfNote{} <- t -> Tick t $ rest expr -- Otherwise we assume that ticks of different placements float -- through each other. - | tickishPlace t2 /= tickishPlace t -> mkTick' (top . Tick t2) rest e + | tickishPlace t2 /= tickishPlace t -> Tick t2 $ mkTick' rest e -- For annotations this is where we make sure to not introduce -- redundant ticks. - | tickishContains t t2 -> mkTick' top rest e - | tickishContains t2 t -> orig_expr - | otherwise -> mkTick' top (rest . Tick t2) e + | tickishContains t t2 -> mkTick' rest e -- Drop t2 + | tickishContains t2 t -> rest e -- Drop t + | otherwise -> mkTick' (rest . Tick t2) e -- Ticks don't care about types, so we just float all ticks -- through them. Note that it's not enough to check for these @@ -343,14 +344,14 @@ mkTick t orig_expr = mkTick' id id orig_expr -- expressions below ticks, such constructs can be the result of -- unfoldings. We therefore make an effort to put everything into -- the right place no matter what we start with. - Cast e co -> mkTick' (top . flip Cast co) rest e - Coercion co -> Coercion co + Cast e co -> mkCast (mkTick' rest e) co + Coercion co -> Tick t $ rest (Coercion co) Lam x e -- Always float through type lambdas. Even for non-type lambdas, -- floating is allowed for all but the most strict placement rule. | not (isRuntimeVar x) || tickishPlace t /= PlaceRuntime - -> mkTick' (top . Lam x) rest e + -> Lam x $ mkTick' rest e -- If it is both counting and scoped, we split the tick into its -- two components, often allowing us to keep the counting tick on @@ -359,25 +360,25 @@ mkTick t orig_expr = mkTick' id id orig_expr -- floated, and the lambda may then be in a position to be -- beta-reduced. | canSplit - -> top $ Tick (mkNoScope t) $ rest $ Lam x $ mkTick (mkNoCount t) e + -> Tick (mkNoScope t) $ rest $ Lam x $ mkTick (mkNoCount t) e App f arg -- Always float through type applications. | not (isRuntimeArg arg) - -> mkTick' (top . flip App arg) rest f + -> App (mkTick' rest f) arg -- We can also float through constructor applications, placement -- permitting. Again we can split. | isSaturatedConApp expr && (tickishPlace t==PlaceCostCentre || canSplit) -> if tickishPlace t == PlaceCostCentre - then top $ rest $ tickHNFArgs t expr - else top $ Tick (mkNoScope t) $ rest $ tickHNFArgs (mkNoCount t) expr + then rest $ tickHNFArgs t expr + else Tick (mkNoScope t) $ rest $ tickHNFArgs (mkNoCount t) expr Var x | notFunction && tickishPlace t == PlaceCostCentre - -> orig_expr + -> rest expr -- Drop t | notFunction && canSplit - -> top $ Tick (mkNoScope t) $ rest expr + -> Tick (mkNoScope t) $ rest expr where -- SCCs can be eliminated on variables provided the variable -- is not a function. In these cases the SCC makes no difference: @@ -389,10 +390,10 @@ mkTick t orig_expr = mkTick' id id orig_expr Lit{} | tickishPlace t == PlaceCostCentre - -> orig_expr + -> rest expr -- Drop t -- Catch-all: Annotate where we stand - _any -> top $ Tick t $ rest expr + _any -> Tick t $ rest expr mkTicks :: [CoreTickish] -> CoreExpr -> CoreExpr mkTicks ticks expr = foldr mkTick expr ticks ===================================== compiler/GHC/Tc/Instance/Class.hs ===================================== @@ -47,6 +47,7 @@ import GHC.Core.Make ( mkCharExpr, mkNaturalExpr, mkStringExprFS, mkCoreLams ) import GHC.Core.DataCon import GHC.Core.TyCon import GHC.Core.Class +import GHC.Core.Utils( mkCast ) import GHC.Core ( Expr(..) ) @@ -456,7 +457,7 @@ matchWithDict [cls, mty] mkCoreLams [ runtimeRep1TyVar, openAlphaTyVar, sv, k ] $ Var k `App` - (Var sv `Cast` mkTransCo (mkSubCo co2) (mkSymCo co)) + (Var sv `mkCast` mkTransCo (mkSubCo co2) (mkSymCo co)) ; tc <- tcLookupTyCon withDictClassName ; let Just withdict_data_con @@ -935,7 +936,7 @@ matchDataToTag dataToTagClass [levity, dty] = do dataToTagDataCon = tyConSingleDataCon (classTyCon dataToTagClass) mk_ev _ = evDataConApp dataToTagDataCon [levity, dty] - [methodRep `Cast` methodCo] + [methodRep `mkCast` methodCo] -> addUsedDataCons rdr_env repTyCon -- See wrinkles DTW2 and DTW3 $> OneInst { cir_new_theta = [] -- (Ignore stupid theta.) , cir_mk_ev = mk_ev ===================================== compiler/GHC/Tc/Solver.hs ===================================== @@ -93,7 +93,7 @@ import Control.Monad import Control.Monad.Trans.Class ( lift ) import Control.Monad.Trans.State.Strict ( StateT(runStateT), put ) import Data.Foldable ( toList, traverse_ ) -import Data.List ( partition, intersect ) +import Data.List ( partition ) import Data.List.NonEmpty ( NonEmpty(..), nonEmpty ) import qualified Data.List.NonEmpty as NE import GHC.Data.Maybe ( isJust, mapMaybe, catMaybes ) @@ -3755,32 +3755,74 @@ Type-class defaulting deals with the situation where we have unsolved constraints like (Num alpha), where `alpha` is a unification variable. We want to pick a default for `alpha`, such as `alpha := Int` to resolve the ambiguity. -Type-class defaulting is guided by the `DefaultEnv`: see Note [Named default declarations] -in GHC.Tc.Gen.Default +The function 'tryTypeClassDefaulting' implements type-class defaulting. The +algorithm for defaulting depends on whether certain extensions are enabled, +such as -XOverloadedStrings or -XExtendedDefaultRules. To explain this, let us +define the following: -The entry point for defaulting the unsolved constraints is `applyDefaultingRules`, -which depends on `disambigGroup`, which in turn depends on workhorse -`disambigProposalSequences`. The latter is also used by defaulting plugins through -`disambigMultiGroup` (see Note [Defaulting plugins] below). + Unary typeclass: + a typeclass with a single visible type argument. -The algorithm works as follows. Let S be the complete set of unsolved -constraints, and initialize Sx to an empty set of constraints. For every type -variable `v` that is free in S: + Examples: -1. Define Cv = { Ci v | Ci v ∈ S }, the subset of S consisting of all constraints in S of - form (Ci v), where Ci is a single-parameter type class. (We do no defaulting for - multi-parameter type classes.) + Num :: Type -> Constraint + Eq :: Type -> Constraint + Foldable :: (Type -> Type) -> Constraint + Typeable :: forall k. k -> Constraint -- NB: also has an /invisible/ argument -2. Define Dv, by extending Cv with the superclasses of every Ci in Cv + Non-examples: -3. Define Ev, by filtering Dv to contain only classes with a default declaration. + Nullary :: Constraint + Binary :: Type -> Type -> Constraint + Binary2 :: forall k -> k -> Constraint -- Two visible arguments -4. For each Ci in Ev, if Ci has a non-empty default list in the `DefaultEnv`, find the first - type T in the default list for Ci for which, for every (Ci v) in Cv, the constraint (Ci T) - is soluble. + Defaultable class + a typeclass which has at least one in-scope default declaration -5. If there is precisely one type T in the resulting type set, resolve the ambiguity by adding - a constraint (v~ Ti) constraint to a set Sx; otherwise report a static error. + This includes the two different categories of default declarations: + + - Haskell 98 default declarations such as 'default (Integer, Float)'. + + - `Num` is always defaultable; either the user says 'default( Integer, Float )' + or (absent such a declaration) the system fills in a fallback default declaration. + See Section 4.3.4 in https://www.haskell.org/onlinereport/haskell2010/haskellch4.html + + - With `OverloadedStrings`, the class `IsString` is defaultable + - With `ExtendedDefaultRules`, the classes `Show`, `Eq`, `Ord`, `Foldable` and `Traversable` + are defaultable + + - Named default declarations, which apply to the named class, e.g. + 'default Cls(X, Y)' applies precisely to 'Cls'. + Note that these may be locally defined, or they may be imported. + + Standard class: + a class defined in the Prelude or the standard library, as defined + by the Haskell 98 report (section 4.3.4) + + These are defined in GHC.Builtin.Names.standardClassKeys. + +The rules for defaulting a collection 'S' of unsolved constraints are as follows: + + 1. For each metavariable 'v' appearing in 'S', define + + U_v = { C v | C v ∈ U, C is a unary typeclass } + + We then process each 'U_v' in turn, in order to find a defaulting + assignment 'v := ty' that solves all of 'U_v'. + + 2. Unless -XExtendedDefaultRules is in effect, give up if 'v' appears: + + - in any constraint that isn't a unary class constraint + - in a class constraint which is non-standard and does not have + a default declaration in scope. + + 3. Compute candidate assignments: for each unary typeclass 'C' in 'U_v' which + has a default declaration in scope, find the first type 'ty' in the list + of in-scope default types for 'C' for which all of 'U_v' is soluble. + + 4. If there is precisely one type candidate type assignment 'ty' that allows + all of 'U_v' to be solved, we default 'v := ty'. Otherwise, do nothing + ('v' remains ambiguous). Note [Defaulting plugins] ~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -3919,8 +3961,8 @@ findDefaultableGroups (default_tys, extended_defaults) wanteds -- Finds unary type-class constraints -- But take account of polykinded classes like Typeable, - -- which may look like (Typeable * (a:*)) (#8931) - -- step (1) in Note [How type-class constraints are defaulted] + -- which may look like (Typeable Type (a:Type)) (#8931) + -- See step (1) in Note [How type-class constraints are defaulted] find_unary :: Ct -> Either (Ct, Class, TyVar) Ct find_unary cc | Just (cls,tys) <- getClassPredTys_maybe (ctPred cc) @@ -3932,21 +3974,42 @@ findDefaultableGroups (default_tys, extended_defaults) wanteds = Left (cc, cls, tv) find_unary cc = Right cc -- Non unary or non dictionary - bad_tvs :: TcTyCoVarSet -- TyVars mentioned by non-unaries - bad_tvs = mapUnionVarSet tyCoVarsOfCt non_unaries + nonunary_tvs :: TcTyCoVarSet -- TyVars mentioned by non-unaries + nonunary_tvs = mapUnionVarSet tyCoVarsOfCt non_unaries cmp_tv (_,_,tv1) (_,_,tv2) = tv1 `compare` tv2 defaultable_tyvar :: TcTyVar -> Bool defaultable_tyvar tv = let b1 = isTyConableTyVar tv -- Note [Avoiding spurious errors] - b2 = not (tv `elemVarSet` bad_tvs) + b2 = not (tv `elemVarSet` nonunary_tvs) in b1 && (b2 || extended_defaults) -- Note [Multi-parameter defaults] - -- Determines if any of the given type class constructors is in default_tys - -- step (3) in Note [How type-class constraints are defaulted] + -- Determines whether the collection of class constraints permits defaulting. + -- See step (2) in Note [How type-class constraints are defaulted] defaultable_classes :: [Class] -> Bool - defaultable_classes clss = not . null . intersect clss $ map cd_class default_tys + defaultable_classes clss = + -- One of the classes has a default declaration in scope + -- (this includes 'Num', and e.g. 'IsString' with -XOverloadedStrings) + any (`elementOfUniqSet` classes_with_defaults) clss + && + -- AND, either: + -- - ExtendedDefaultRules is in effect, or + -- - all the classes are standard or have a default declaration in scope + (extended_defaults || all is_std_or_has_default clss) + is_std_or_has_default :: Class -> Bool + is_std_or_has_default cls = + (getUnique cls `elem` standardClassKeys) + || + (cls `elementOfUniqSet` classes_with_defaults) + + -- All classes with a default declaration in scope; either: + -- + -- - a named default declaration such as 'default C(Double, Bool)', or + -- - a Haskell 98 default declaration such as 'default(Int, Float)', + -- which adds defaults for Num, for IsString with OverloadedStrings, + -- and for Foldable/Traversable/... with ExtendedDefaultRules + classes_with_defaults = mkUniqSet $ map cd_class default_tys ------------------------------ @@ -3996,14 +4059,14 @@ disambigProposalSequences orig_wanteds wanteds proposalSequences allConsistent = do { traverse_ (traverse_ reportInvalidDefaultedTyVars . getProposalSequence) proposalSequences ; fake_ev_binds_var <- TcS.newTcEvBinds ; tclvl <- TcS.getTcLevel - -- Step (4) in Note [How type-class constraints are defaulted] + -- Step (3) in Note [How type-class constraints are defaulted] ; successes <- fmap catMaybes $ nestImplicTcS fake_ev_binds_var (pushTcLevel tclvl) $ mapM firstSuccess proposalSequences ; traceTcS "disambigProposalSequences" (vcat [ ppr wanteds , ppr proposalSequences , ppr successes ]) - -- Step (5) in Note [How type-class constraints are defaulted] + -- Step (4) in Note [How type-class constraints are defaulted] ; case successes of success@(tvs, subst) : rest | allConsistent (success :| rest) ===================================== compiler/GHC/Tc/Solver/Dict.hs ===================================== @@ -102,28 +102,53 @@ solveDict dict_ct@(DictCt { di_ev = ev, di_cls = cls, di_tys = tys }) ; stopWithStage (dictCtEvidence dict_ct) "Kept inert DictCt" } updInertDicts :: DictCt -> TcS () -updInertDicts dict_ct@(DictCt { di_cls = cls, di_ev = ev, di_tys = tys }) - = do { traceTcS "Adding inert dict" (ppr dict_ct $$ ppr cls <+> ppr tys) - - ; if | isGiven ev, Just (str_ty, _) <- isIPPred_maybe cls tys - -> -- See (SIP1) and (SIP2) in Note [Shadowing of implicit parameters] - -- Update /both/ inert_cans /and/ inert_solved_dicts. - updInertSet $ \ inerts@(IS { inert_cans = ics, inert_solved_dicts = solved }) -> - inerts { inert_cans = updDicts (filterDicts (does_not_mention_ip_for str_ty)) ics - , inert_solved_dicts = filterDicts (does_not_mention_ip_for str_ty) solved } - | otherwise - -> return () +updInertDicts dict_ct + = do { traceTcS "Adding inert dict" (ppr dict_ct) + + -- For Given implicit parameters (only), delete any existing + -- Givens for the same implicit parameter. + -- See Note [Shadowing of implicit parameters] + ; deleteGivenIPs dict_ct -- Add the new constraint to the inert set ; updInertCans (updDicts (addDict dict_ct)) } + +deleteGivenIPs :: DictCt -> TcS () +-- Special magic when adding a Given implicit parameter to the inert set +-- For [G] ?x::ty, remove any existing /Givens/ mentioning ?x, +-- from /both/ inert_cans /and/ inert_solved_dicts (#23761) +-- See Note [Shadowing of implicit parameters] +deleteGivenIPs (DictCt { di_cls = cls, di_ev = ev, di_tys = tys }) + | isGiven ev + , Just (str_ty, _) <- isIPPred_maybe cls tys + = updInertSet $ \ inerts@(IS { inert_cans = ics, inert_solved_dicts = solved }) -> + inerts { inert_cans = updDicts (filterDicts (keep_can str_ty)) ics + , inert_solved_dicts = filterDicts (keep_solved str_ty) solved } + | otherwise + = return () where - -- Does this class constraint or any of its superclasses mention - -- an implicit parameter (?str :: ty) for the given 'str' and any type 'ty'? - does_not_mention_ip_for :: Type -> DictCt -> Bool - does_not_mention_ip_for str_ty (DictCt { di_cls = cls, di_tys = tys }) - = not $ mentionsIP (not . typesAreApart str_ty) (const True) cls tys - -- See Note [Using typesAreApart when calling mentionsIP] - -- in GHC.Core.Predicate + keep_can, keep_solved :: Type -> DictCt -> Bool + -- keep_can: we keep an inert dictionary UNLESS + -- (1) it is a Given + -- (2) it binds an implicit parameter (?str :: ty) for the given 'str' + -- regardless of 'ty', possibly via its superclasses + -- The test is a bit conservative, hence `mentionsIP` and `typesAreApart` + -- See Note [Using typesAreApart when calling mentionsIP] + -- in GHC.Core.Predicate + -- + -- keep_solved: same as keep_can, but for /all/ constraints not just Givens + -- + -- Why two functions? See (SIP3) in Note [Shadowing of implicit parameters] + keep_can str (DictCt { di_ev = ev, di_cls = cls, di_tys = tys }) + = not (isGiven ev -- (1) + && mentions_ip str cls tys) -- (2) + keep_solved str (DictCt { di_cls = cls, di_tys = tys }) + = not (mentions_ip str cls tys) + + -- mentions_ip: the inert constraint might provide evidence + -- for an implicit parameter (?str :: ty) for the given 'str' + mentions_ip str cls tys + = mentionsIP (not . typesAreApart str) (const True) cls tys canDictCt :: CtEvidence -> Class -> [Type] -> SolverStage DictCt -- Once-only processing of Dict constraints: @@ -220,7 +245,9 @@ in two places: * In `updInertDicts`, in this module, when adding [G] (?x :: ty), remove any existing [G] (?x :: ty'), regardless of ty'. -* Wrinkle (SIP1): we must be careful of superclasses. Consider +There are wrinkles: + +* Wrinkle (SIP1): we must be careful of superclasses (#14218). Consider f,g :: (?x::Int, C a) => a -> a f v = let ?x = 4 in g v @@ -228,24 +255,31 @@ in two places: We must /not/ solve this from the Given (?x::Int, C a), because of the intervening binding for (?x::Int). #14218. - We deal with this by arranging that when we add [G] (?x::ty) we delete + We deal with this by arranging that when we add [G] (?x::ty) we /delete/ * from the inert_cans, and * from the inert_solved_dicts any existing [G] (?x::ty) /and/ any [G] D tys, where (D tys) has a superclass with (?x::ty). See Note [Local implicit parameters] in GHC.Core.Predicate. - An important special case is constraint tuples like [G] (% ?x::ty, Eq a %). - But it could happen for `class xx => D xx where ...` and the constraint D - (?x :: int). This corner (constraint-kinded variables instantiated with - implicit parameter constraints) is not well explored. + An very important special case is constraint tuples like [G] (% ?x::ty, Eq a %). + + But it could also happen for `class xx => D xx where ...` and the constraint + D (?x :: int); again see Note [Local implicit parameters]. This corner + (constraint-kinded variables instantiated with implicit parameter constraints) + is not well explored. - Example in #14218, and #23761 + You might worry about whether deleting an /entire/ constraint just because + a distant superclass has an implicit parameter might make another Wanted for + that constraint un-solvable. Indeed so. But for constraint tuples it doesn't + matter -- their entire payload is their superclasses. And the other case is + the ill-explored corner above. The code that accounts for (SIP1) is in updInertDicts; in particular the call to GHC.Core.Predicate.mentionsIP. * Wrinkle (SIP2): we must apply this update semantics for `inert_solved_dicts` - as well as `inert_cans`. + as well as `inert_cans` (#23761). + You might think that wouldn't be necessary, because an element of `inert_solved_dicts` is never an implicit parameter (see Note [Solved dictionaries] in GHC.Tc.Solver.InertSet). @@ -258,6 +292,19 @@ in two places: Now (C (?x::Int)) has a superclass (?x::Int). This may look exotic, but it happens particularly for constraint tuples, like `(% ?x::Int, Eq a %)`. +* Wrinkle (SIP3) + - Note that for the inert dictionaries, `inert_cans`, we must /only/ delete + existing /Givens/! Deleting an existing Wanted led to #26451; we just never + solved it! + + - In contrast, the solved dictionaries, `inert_solved_dicts`, are really like + Givens; they may be "inherited" from outer scopes, so we must delete any + solved dictionaries for this implicit parameter for /both/ Givens /and/ + Wanteds. + + Otherwise the new Given doesn't properly shadow those inherited solved + dictionaries. Test T23761 showed this up. + Example 1: Suppose we have (typecheck/should_compile/ImplicitParamFDs) ===================================== compiler/GHC/Tc/Types/Evidence.hs ===================================== @@ -56,6 +56,7 @@ import GHC.Types.Var import GHC.Types.Id( idScaledType ) import GHC.Core.Coercion.Axiom import GHC.Core.Coercion +import GHC.Core.Utils( mkCast ) import GHC.Core.Ppr () -- Instance OutputableBndr TyVar import GHC.Tc.Utils.TcType import GHC.Core.Type @@ -528,7 +529,7 @@ evCoercion co = EvExpr (Coercion co) -- | d |> co evCast :: EvExpr -> TcCoercion -> EvTerm evCast et tc | isReflCo tc = EvExpr et - | otherwise = EvExpr (Cast et tc) + | otherwise = EvExpr (mkCast et tc) -- Dictionary instance application evDFunApp :: DFunId -> [Type] -> [EvExpr] -> EvTerm ===================================== compiler/GHC/Types/DefaultEnv.hs ===================================== @@ -31,9 +31,13 @@ import Data.List (sortBy) import Data.Function (on) -- See Note [Named default declarations] in GHC.Tc.Gen.Default + -- | Default environment mapping class name @Name@ to their default type lists +-- +-- NB: this includes Haskell98 default declarations, at the 'Num' key. type DefaultEnv = NameEnv ClassDefaults +-- | Defaulting type assignments for the given class. data ClassDefaults = ClassDefaults { cd_class :: Class -- ^ The class whose defaults are being defined , cd_types :: [Type] ===================================== docs/users_guide/9.12.4-notes.rst ===================================== @@ -0,0 +1,154 @@ +.. _release-9-12-4: + +Version 9.12.4 +============== + +The significant changes to the various parts of the compiler are listed in the +following sections. See the `migration guide +<https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.12>`_ on the GHC Wiki +for specific guidance on migrating programs to this release. + +Compiler +~~~~~~~~ + +- Fixed a bug in CSE where the in-scope set was not properly maintained (:ghc-ticket:`25468`) +- Fixed ``matchExpectedFunTys`` to use ``tcMkScaledFunTys`` (:ghc-ticket:`26277`) +- Fixed ``parenBreakableList`` usage in ``ppHsContext`` for better pretty-printing of contexts +- Improved error messages for bad record updates to allow out-of-scope data constructors (:ghc-ticket:`26391`) +- Fixed a missing InVar->OutVar lookup in ``SetLevels`` (:ghc-ticket:`26681`) +- Fixed split sections on Windows (:ghc-ticket:`26696`, :ghc-ticket:`26494`) +- Fixed split sections for the LLVM backend (:ghc-ticket:`26770`) +- Don't re-use stack slots for growing registers (:ghc-ticket:`26668`) +- Fixed cast worker/wrapper incorrectly firing on INLINE functions (:ghc-ticket:`26903`) +- Fixed non-determinism in ``TyLitMap`` by using deterministic maps for strings (:ghc-ticket:`26846`) +- Fixed non-determinism in ``WithHsDocIdentifiers`` binary instance by using a stable sort (:ghc-ticket:`26858`) +- Added ``-mcmodel=medium`` module flag to generated LLVM IR on LoongArch +- Pass the ``mcmodel=medium`` parameter to CC via GHC on LoongArch +- Pass the ``+evex512`` attribute to LLVM 18+ when ``-mavx512f`` is set (:ghc-ticket:`26410`) +- Improved error handling in ``getPackageArchives`` (:ghc-ticket:`26383`) +- Fixed a shadowing bug in implicit parameters (:ghc-ticket:`26451`) +- Fixed a subtle bug in ``GHC.Core.Utils.mkTick`` that could generate type-incorrect code (:ghc-ticket:`26772`) +- Fixed a long-standing interaction between ticks and casts in ``Eliminate Identity Cases`` +- ``NamedDefaults``: require the class to be standard or have an in-scope default declaration (:ghc-ticket:`25775`, :ghc-ticket:`25778`) + +Runtime System +~~~~~~~~~~~~~~ + +- Fixed a deadlock with eventlog flush interval and RTS shutdown (:ghc-ticket:`26573`) +- Fixed eager black holes: record mutated closure and fix assertion (:ghc-ticket:`26495`) +- Fixed object file format detection in ``loadArchive`` (:ghc-ticket:`26630`) +- Use ``INFO_TABLE_CONSTR`` for ``stg_dummy_ret_closure`` (:ghc-ticket:`26745`) +- Fixed lost wakeups in ``threadPaused`` for threads blocked on black holes (:ghc-ticket:`26324`) +- Fixed ``stg_AP_STACK`` to push the correct update frame (:ghc-ticket:`26324`) +- Fixed potential loop in heap reservation logic on certain kernels (:ghc-ticket:`26151`) +- Don't use CAS without ``PARALLEL_GC`` on +- Switch prim to use modern atomic compiler builtins (:ghc-ticket:`26729`) +- Removed obsolete ``CC_SUPPORTS_TLS``, ``HAS_VISIBILITY_HIDDEN``, ``COMPILING_WINDOWS_DLL``, + and ``__GNUC__``-related logic +- Removed the ``-O3`` pragma hack in ``Hash.c`` +- Removed unnecessary Cabal flags + +Code Generation +~~~~~~~~~~~~~~~ + +- NCG for PPC: add pattern for ``CmmRegOff`` to ``iselExpr64`` (:ghc-ticket:`26828`) +- PPC NCG: Use libcall for 64-bit ``cmpxchg`` on 32-bit PowerPC (:ghc-ticket:`23969`) + +Bytecode Compiler +~~~~~~~~~~~~~~~~~ + +- Use 32 bits for breakpoint index (:ghc-ticket:`26325`) + +``base`` library +~~~~~~~~~~~~~~~~ + +- Expose ``Backtraces`` constructor and fields (:ghc-ticket:`26049`) +- Store ``StackTrace`` and ``StackSnapshot`` in ``Backtraces``, deferring decoding until display +- Evaluate backtraces for ``error`` exceptions at the moment they are thrown + (`CLC proposal #383 <https://github.com/haskell/core-libraries-committee/issues/383>`__, + :ghc-ticket:`26751`) + +``ghc-experimental`` library +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +- Fixed ``GHC.Exception.Backtrace.Experimental`` module +- Added ability to customise the collection of exception annotations + +``ghc-pkg`` +~~~~~~~~~~~~ + +- Removed ``traceId`` from ``ghc-pkg`` executable + +``ghc-toolchain`` +~~~~~~~~~~~~~~~~~ + +- Dropped ``ld.gold`` from merge object command + +Build System +~~~~~~~~~~~~ + +- Added ``hpc`` to release script +- Use a response file to invoke GHC when analysing dependencies +- Fixed ``GHC.Platform.Host`` generation for cross stage1 (:ghc-ticket:`26449`) +- Fixed runtime error during ``users_guide`` build with Sphinx 9.1.0 (:ghc-ticket:`26810`) +- Added ``ghc-{experimental,internal}.cabal`` to the list of dependencies of the doc target (:ghc-ticket:`26738`) + +Wasm Backend +~~~~~~~~~~~~ + +- Fixed dyld handling for forward declared ``GOT.func`` items (:ghc-ticket:`26430`) +- Ensure ``setKeepCAFs()`` is called in GHCi (:ghc-ticket:`26106`) +- Prevent bundlers from resolving ``import("node:timers")`` +- Use ``import.meta.main`` for proper distinction of Node.js main modules (:ghc-ticket:`26916`) + +Included libraries +~~~~~~~~~~~~~~~~~~ + +The package database provided with this distribution also contains a number of +packages other than GHC itself. See the changelogs provided with these packages +for further change information. + +.. ghc-package-list:: + + compiler/ghc.cabal: The compiler itself + libraries/array/array.cabal: Dependency of ``ghc`` library + libraries/base/base.cabal: Core library + libraries/binary/binary.cabal: Dependency of ``ghc`` library + libraries/bytestring/bytestring.cabal: Dependency of ``ghc`` library + libraries/Cabal/Cabal/Cabal.cabal: Dependency of ``ghc-pkg`` utility + libraries/Cabal/Cabal-syntax/Cabal-syntax.cabal: Dependency of ``ghc-pkg`` utility + libraries/containers/containers/containers.cabal: Dependency of ``ghc`` library + libraries/deepseq/deepseq.cabal: Dependency of ``ghc`` library + libraries/directory/directory.cabal: Dependency of ``ghc`` library + libraries/exceptions/exceptions.cabal: Dependency of ``ghc`` and ``haskeline`` library + libraries/file-io/file-io.cabal: Dependency of ``directory`` library + libraries/filepath/filepath.cabal: Dependency of ``ghc`` library + libraries/ghc-boot/ghc-boot.cabal: Internal compiler library + libraries/ghc-boot-th/ghc-boot-th.cabal: Internal compiler library + libraries/ghc-compact/ghc-compact.cabal: Core library + libraries/ghc-experimental/ghc-experimental.cabal: Core library + libraries/ghc-heap/ghc-heap.cabal: GHC heap-walking library + libraries/ghci/ghci.cabal: The REPL interface + libraries/ghc-internal/ghc-internal.cabal: Core library + libraries/ghc-platform/ghc-platform.cabal: Internal library + libraries/ghc-prim/ghc-prim.cabal: Core library + libraries/haskeline/haskeline.cabal: Dependency of ``ghci`` executable + libraries/hpc/hpc.cabal: Dependency of ``hpc`` executable + libraries/integer-gmp/integer-gmp.cabal: Core library + libraries/mtl/mtl.cabal: Dependency of ``Cabal`` library + libraries/os-string/os-string.cabal: Dependency of ``filepath`` library + libraries/parsec/parsec.cabal: Dependency of ``Cabal`` library + libraries/pretty/pretty.cabal: Dependency of ``ghc`` library + libraries/process/process.cabal: Dependency of ``ghc`` library + libraries/semaphore-compat/semaphore-compat.cabal: Dependency of ``ghc`` library + libraries/stm/stm.cabal: Dependency of ``haskeline`` library + libraries/template-haskell/template-haskell.cabal: Core library + libraries/terminfo/terminfo.cabal: Dependency of ``haskeline`` library + libraries/text/text.cabal: Dependency of ``Cabal`` library + libraries/time/time.cabal: Dependency of ``ghc`` library + libraries/transformers/transformers.cabal: Dependency of ``ghc`` library + libraries/unix/unix.cabal: Dependency of ``ghc`` library + libraries/Win32/Win32.cabal: Dependency of ``ghc`` library + libraries/xhtml/xhtml.cabal: Dependency of ``haddock`` executable + utils/haddock/haddock-api/haddock-api.cabal: Dependency of ``haddock`` executable + utils/haddock/haddock-library/haddock-library.cabal: Dependency of ``haddock`` executable ===================================== docs/users_guide/release-notes.rst ===================================== @@ -7,3 +7,4 @@ Release notes 9.12.1-notes 9.12.2-notes 9.12.3-notes + 9.12.4-notes ===================================== libraries/base/base.cabal.in ===================================== @@ -4,7 +4,7 @@ cabal-version: 3.0 -- Make sure you are editing ghc-experimental.cabal.in, not ghc-experimental.cabal name: base -version: 4.21.1.0 +version: 4.21.2.0 -- NOTE: Don't forget to update ./changelog.md license: BSD-3-Clause ===================================== libraries/base/changelog.md ===================================== @@ -1,7 +1,9 @@ # Changelog for [`base` package](http://hackage.haskell.org/package/base) -## 4.21.2.0 *TBA* - * Evaluate backtraces for "error" exceptions at the moment they are thrown. ([CLC proposal #383](https://github.com/haskell/core-libraries-committee/issues/383)) +## 4.21.2.0 *March 2026* + * Expose `Backtraces` constructor and fields ([CLC proposal #199](https://github.com/haskell/core-libraries-committee/issues/199), [#26049](https://gitlab.haskell.org/ghc/ghc/-/issues/26049)) + * Store `StackTrace` and `StackSnapshot` in `Backtraces`, deferring decoding until display + * Evaluate backtraces for "error" exceptions at the moment they are thrown ([CLC proposal #383](https://github.com/haskell/core-libraries-committee/issues/383), [#26751](https://gitlab.haskell.org/ghc/ghc/-/issues/26751)) ## 4.21.1.0 *Sept 2024* * Fix incorrect results of `integerPowMod` when the base is 0 and the exponent is negative, and `integerRecipMod` when the modulus is zero ([#26017](https://gitlab.haskell.org/ghc/ghc/-/issues/26017)). ===================================== rts/Disassembler.c ===================================== @@ -87,12 +87,12 @@ disInstr ( StgBCO *bco, int pc ) case bci_BRK_FUN: debugBelch ("BRK_FUN " ); printPtr( ptrs[instrs[pc]] ); debugBelch (" %d ", instrs[pc+1]); printPtr( ptrs[instrs[pc+2]] ); - CostCentre* cc = (CostCentre*)literals[instrs[pc+5]]; + CostCentre* cc = (CostCentre*)literals[instrs[pc+7]]; if (cc) { debugBelch(" %s", cc->label); } debugBelch("\n"); - pc += 6; + pc += 8; break; case bci_SWIZZLE: { W_ stkoff = BCO_GET_LARGE_ARG; ===================================== rts/Interpreter.c ===================================== @@ -1286,8 +1286,8 @@ run_BCO: arg1_brk_array = BCO_GET_LARGE_ARG; arg2_tick_mod = BCO_GET_LARGE_ARG; arg3_info_mod = BCO_GET_LARGE_ARG; - arg4_tick_index = BCO_NEXT; - arg5_info_index = BCO_NEXT; + arg4_tick_index = BCO_READ_NEXT_32; + arg5_info_index = BCO_READ_NEXT_32; #if defined(PROFILING) arg6_cc = BCO_GET_LARGE_ARG; #else ===================================== testsuite/tests/default/T25775.hs ===================================== @@ -0,0 +1,19 @@ + + +module T25775 where + +import Data.Kind + +default (Int) + +type NonStd :: Type -> Constraint +class NonStd a where + +f :: (Num a, NonStd a) => a -> a +f = (+1) + +x :: String +x = show (f 0) + -- We should NOT default 0 to type Int, despite the top-level default + -- declaration in this module, because of the presence of the + -- non-standard class 'NonStd'. ===================================== testsuite/tests/default/T25775.stderr ===================================== @@ -0,0 +1,19 @@ +T25775.hs:16:5: error: [GHC-39999] + • Ambiguous type variable ‘a0’ arising from a use of ‘show’ + prevents the constraint ‘(Show a0)’ from being solved. + Probable fix: use a type annotation to specify what ‘a0’ should be. + Potentially matching instances: + instance Show Ordering -- Defined in ‘GHC.Internal.Show’ + instance Show Integer -- Defined in ‘GHC.Internal.Show’ + ...plus 25 others + ...plus 13 instances involving out-of-scope types + (use -fprint-potential-instances to see them all) + • In the expression: show (f 0) + In an equation for ‘x’: x = show (f 0) + +T25775.hs:16:11: error: [GHC-39999] + • No instance for ‘NonStd a0’ arising from a use of ‘f’ + • In the first argument of ‘show’, namely ‘(f 0)’ + In the expression: show (f 0) + In an equation for ‘x’: x = show (f 0) + ===================================== testsuite/tests/default/all.T ===================================== @@ -30,6 +30,7 @@ test('default-fail05', normal, compile_fail, ['']) test('default-fail06', normal, compile_fail, ['']) test('default-fail07', normal, compile_fail, ['']) test('default-fail08', normal, compile_fail, ['']) +test('T25775', normal, compile_fail, ['']) test('T25206', [extra_files(['T25206_helper.hs'])], multimod_compile, ['T25206', '']) test('T25858', normal, compile_and_run, ['']) test('T25858v1', [extra_files(['T25858v1_helper.hs'])], multimod_compile_and_run, ['T25858v1', '']) ===================================== testsuite/tests/typecheck/should_compile/T26451.hs ===================================== @@ -0,0 +1,34 @@ +{-# LANGUAGE ImplicitParams, TypeFamilies, FunctionalDependencies, ScopedTypeVariables #-} + +module T26451 where + +type family F a +type instance F Bool = [Char] + +class C a b | b -> a +instance C Bool Bool +instance C Char Char + +eq :: forall a b. C a b => a -> b -> () +eq p q = () + +g :: a -> F a +g = g + +f (x::tx) (y::ty) -- x :: alpha y :: beta + = let ?v = g x -- ?ip :: F alpha + in (?v::[ty], eq x True) + + +{- tx, and ty are unification variables + +Inert: [G] dg :: IP "v" (F tx) + [W] dw :: IP "v" [ty] +Work-list: [W] dc1 :: C tx Bool + [W] dc2 :: C ty Char + +* Solve dc1, we get tx := Bool from fundep +* Kick out dg +* Solve dg to get [G] dc : IP "v" [Char] +* Add that new dg to the inert set: that simply deletes dw!!! +-} ===================================== testsuite/tests/typecheck/should_compile/all.T ===================================== @@ -938,3 +938,4 @@ test('T23501b', normal, compile, ['']) test('T25597', normal, compile, ['']) test('T25960', normal, compile, ['']) test('T26256a', normal, compile, ['']) +test('T26451', normal, compile, ['']) ===================================== testsuite/tests/typecheck/should_fail/T12921.stderr ===================================== @@ -1,3 +1,34 @@ +T12921.hs:4:1: error: [GHC-39999] + • Ambiguous type variable ‘a0’ arising from an annotation + prevents the constraint ‘(GHC.Internal.Data.Data.Data + a0)’ from being solved. + Probable fix: use a type annotation to specify what ‘a0’ should be. + Potentially matching instances: + instance (GHC.Internal.Data.Data.Data a, + GHC.Internal.Data.Data.Data b) => + GHC.Internal.Data.Data.Data (Either a b) + -- Defined in ‘GHC.Internal.Data.Data’ + instance GHC.Internal.Data.Data.Data Ordering + -- Defined in ‘GHC.Internal.Data.Data’ + ...plus 17 others + ...plus 49 instances involving out-of-scope types + (use -fprint-potential-instances to see them all) + • In the annotation: + {-# ANN module "HLint: ignore Reduce duplication" #-} + +T12921.hs:4:16: error: [GHC-39999] + • Ambiguous type variable ‘a0’ arising from the literal ‘"HLint: ignore Reduce duplication"’ + prevents the constraint ‘(GHC.Internal.Data.String.IsString + a0)’ from being solved. + Probable fix: use a type annotation to specify what ‘a0’ should be. + Potentially matching instance: + instance (a ~ Char) => GHC.Internal.Data.String.IsString [a] + -- Defined in ‘GHC.Internal.Data.String’ + ...plus two instances involving out-of-scope types + (use -fprint-potential-instances to see them all) + • In the annotation: + {-# ANN module "HLint: ignore Reduce duplication" #-} T12921.hs:7:8: error: [GHC-88464] Variable not in scope: choice :: [a0] -> Int -> Int + View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/9930dbc4e69ce154c81f3f99209d55… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/9930dbc4e69ce154c81f3f99209d55… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/backports-9.12.4] 7 commits: Report solid equality errors before custom errors
by Zubin (＠wz1000) 03 Mar '26

03 Mar '26

Zubin pushed to branch wip/backports-9.12.4 at Glasgow Haskell Compiler / GHC Commits: 741a4ff3 by Simon Peyton Jones at 2026-03-04T10:52:43+05:30 Report solid equality errors before custom errors This MR fixes #26255 by * Reporting solid equality errors like Int ~ Bool before "custom type errors". See comments in `report1` in `reportWanteds` * Suppressing errors that arise from superclasses of Wanteds. See (SCE1) in Note [Suppressing confusing errors] More details in #26255. (cherry picked from commit ba210d981b0812aea604f884d3c0aada4c8ca75c) - - - - - 2050c915 by Simon Peyton Jones at 2026-03-04T10:52:43+05:30 Fix a horrible shadowing bug in implicit parameters Fixes #26451. The change is in GHC.Tc.Solver.Monad.updInertDicts where we now do /not/ delete /Wanted/ implicit-parameeter constraints. This bug has been in GHC since 9.8! But it's quite hard to provoke; I contructed a tests in T26451, but it was hard to do so. (cherry picked from commit c052c724d2dfc994994b6548545836969aee8ed8) - - - - - c15e880f by Simon Peyton Jones at 2026-03-04T10:52:43+05:30 Fix subtle bug in GHC.Core.Utils.mkTick This patch fixes a decade-old bug in `mkTick`, which could generate type-incorrect code! See the diagnosis in #26772. The new code is simpler and easier to understand. (As #26772 says, I think it could be improved further.) (cherry picked from commit cbe4300ef586c8bee1800426624db12e0237c6b5) - - - - - a9805db7 by Simon Peyton Jones at 2026-03-04T10:52:43+05:30 Fix long-standing interaction between ticks and casts The code for Note [Eliminate Identity Cases] was simply wrong when ticks and casts interacted. This patch fixes the interaction. It was shown up when validating #26772, although it's not the exactly the bug that's reported by #26772. Nor is it easy to reproduce, hence no regression test. (cherry picked from commit b579dfdc614e288b0fd754ac69ae7ff723d808be) - - - - - bbe53332 by sheaf at 2026-03-04T10:52:43+05:30 NamedDefaults: require the class to be standard We now only default type variables if they only appear in constraints of the form `C v`, where `C` is either a standard class or a class with an in-scope default declaration. This rectifies an oversight in the original implementation of the NamedDefault extensions that was remarked in #25775; that implementation allowed type variables to appear in unary constraints which had arbitrary classes at the head. See the rewritten Note [How type-class constraints are defaulted] for details of the implementation. Fixes #25775 Fixes #25778 (cherry picked from commit f1acdd2c2b664ad0bdcaae4064b50e84aa7bc599) - - - - - b9826bf5 by Rodrigo Mesquita at 2026-03-04T10:52:43+05:30 bytecode: Use 32bits for breakpoint index Fixes #26325 (cherry picked from commit e368e24779f8a7bf110a025383db23521b313407) - - - - - 9930dbc4 by Zubin Duggal at 2026-03-04T10:52:43+05:30 Prepare release 9.12.4 - - - - - 35 changed files: - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Instance/Class.hs - compiler/GHC/Tc/Solver.hs - compiler/GHC/Tc/Solver/Dict.hs - compiler/GHC/Tc/Types/Constraint.hs - compiler/GHC/Tc/Types/Evidence.hs - compiler/GHC/Tc/Utils/TcType.hs - compiler/GHC/Types/DefaultEnv.hs - + docs/users_guide/9.12.4-notes.rst - docs/users_guide/release-notes.rst - libraries/base/base.cabal.in - libraries/base/changelog.md - rts/Disassembler.c - rts/Interpreter.c - + testsuite/tests/default/T25775.hs - + testsuite/tests/default/T25775.stderr - testsuite/tests/default/all.T - + testsuite/tests/typecheck/should_compile/T26451.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/T12921.stderr - testsuite/tests/typecheck/should_fail/T18851.hs - + testsuite/tests/typecheck/should_fail/T26255a.hs - + testsuite/tests/typecheck/should_fail/T26255a.stderr - + testsuite/tests/typecheck/should_fail/T26255b.hs - + testsuite/tests/typecheck/should_fail/T26255b.stderr - + testsuite/tests/typecheck/should_fail/T26255c.hs - + testsuite/tests/typecheck/should_fail/T26255c.stderr - testsuite/tests/typecheck/should_fail/UnliftedNewtypesFamilyKindFail2.stderr - testsuite/tests/typecheck/should_fail/all.T The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/538ea5698b993e8f8ae5e40ec27694… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/538ea5698b993e8f8ae5e40ec27694… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/int-index/out-of-scope
by Vladislav Zavialov (＠int-index) 03 Mar '26

03 Mar '26

Vladislav Zavialov pushed new branch wip/int-index/out-of-scope at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/int-index/out-of-scope You're receiving this email because of your account on gitlab.haskell.org.

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